Certain metallic alloy compositions are known for their magnetic properties. Various applications exist for the use of such alloys within industry. The rapidly expanding use of such alloys has also extended into such markets as electronic article surveillance systems. Many of these newer markets require alloys with superior magnetic properties at reduced costs such that the items within which they are employed can be discarded subsequent to their use.
The metallic alloy compositions that constitute permanent magnets are characterized by various performance properties such as coercive level, H.sub.c, and residual induction, B.sub.r. The coercive level is a measure of the resistance of the magnet to demagnetization and the residual induction is a measure of the level of induction possessed by a magnet after saturation and removal of the magnetic field.
Superior magnetic properties can be obtained by using a ferrous alloy containing chromium and cobalt. However, the presence of cobalt typically makes such alloys prohibitively expensive and thus impractical in various end uses.
Certain of the newer magnetic markets further require the preparation of the alloy into a relatively thin strip of material such that the magnetic properties are provided in an economical fashion. As the demand for increasingly thin magnetic strips increases, the selection of metallic alloys possessing the required magnetic properties while also possessing the necessary machinability and workability characteristics to provide the desired shapes, becomes exceedingly difficult. For example, ferrous alloys having carbon contents of about 1 weight percent and chromium contents of about 3-5 weight percent have been shown to exhibit advantageous magnetic properties. However these alloys are mechanically hard and cannot be rolled easily to the required thickness due to either initial hardness or high levels of work hardening during processing.
A need therefore exists in the permanent magnet art for thin magnetic strips having superior magnetic properties without the need for cobalt and other expensive components in the alloy compositions constituting the magnetic strip. The magnetic strips should be made from alloy compositions which are amenable to processing of the alloy into the thin strips required by many industrial uses, especially those below about 0.005 inches in thickness.